*2.1. Study Area*

Yellow River, the second-largest river in China, originates in the Yueguzonglie Basin at the northern foot of the Bayan Khara Mountains in Qinghai. Its main stream is 5464 km long, flowing through nine provinces and regions in China—namely, Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan, and Shandong—and finally running into the Bohai Sea. The Yellow River is regarded as the mother river of China, as Chinese civilization was born in the Yellow River Basin, which is also an important ecological barrier and economic zone in China. The Yellow River Basin covers an area of about 795,000 km2, located between 95◦59 –118◦58 E and 31◦56 –42◦03 N (Figure 1). It amounts to 8.3% of China's land area, and the total population of provinces in which the Yellow River Basin is located was 420 million in 2018, accounting for 30.3% of China's population, with a regional gross national product of over 23.9 trillion yuan, making up 26.5% of China's GDP in 2018. Known as the "energy basin", the Yellow River Basin is rich in coal, oil, natural gas, and non-ferrous metals, among which coal reserves account for

more than half of China's total amount, making it an important base for energy, chemical, raw material, and basic industrial production in China. At the same time, the Yellow River Basin connects the Qinghai–Tibet Plateau, the Loess Plateau, and the North China Plain, and has many national parks and national key ecological function areas such as the Sanjiangyuan and Qilian Mountains, making it an important ecological security barrier in northern China.

In recent years, the rapid industrialization and urbanization of the Yellow River Basin have accelerated the evolution of its natural geographic pattern, and the unreasonable human development and utilization activities have aggravated the deterioration of the ecological environment, resulting in the tightening of resource and environmental constraints in the basin, and the intensity of territorial space development is on the verge of overload. Since industries in the Yellow River Basin rely heavily on energy, and economic zones and urban agglomerations generally use land carelessly, the encroachment of production and living spaces on ecological space is serious, and the problem of spatial conflict of PLES is very prominent, which seriously restricts the high-quality socio-economic development. To achieve the strategic goal of ecological priority and green development, scientific implementation of territorial planning and land-use control and optimization of spatial development and protection pattern are first required to identify the spatio-temporal pattern of spatial conflict of PLES in the Yellow River Basin.

**Figure 1.** Location of the Yellow River Basin.
